Front wall for a stock head box



1961 E. o. MUS'IIONEN 2,993,538

FRONT WALL FOR A STOCK HEAD BOX Filed Nov. 10, 1959 In V 11 I (B Ir/r/(i Nusfmzn )IWMJMQQM fi'liys United States Patent 2,993,538 FRONT WALL FOR A STOCK HEAD BOX Erkki Olavi Mustonen, Helsinki, Finland, assignor to Wartsila-Yhtyma Oy-Wartsila-Koncernen Ab, Helsingfors, Finland, a joint-stock company Filed Nov. 10, 1959, Ser. No. 852,117 Claims priority, application Finland Nov. 10, 1958 1 Claim. (Cl. 162-347) This invention relates to the front wall for a stock head box, especially a high pressure head box, adapted to regulate the stock stream flowing through a slice outlet onto the forming wire of machines such as a paper or a pulp machine.

The necessity of regulating the stock stream flowing from the head box onto said wire is due to the following reasons: The thickness of the stock stream must be adjustable; the stock stream must be parallel with the forming wire or it must be directable against the wire at a desired angle. The stock stream must also meet the forming wire at a certain point with respect to the breast roll.

These requirements may be obtained in many different ways with the aid of a vertical slice unit. In certain conventional types of head boxes the front wall of the stock head box is movable and whilst the apron at the slice outlet as well as the breast roll are fixed. At such head boxes the adjustment is carried out in the following way:

The thickness of the stock stream is adjusted by raising or lowering the front wall of the head box. The stock stream is led out parallel with the forming wire and directed against it at a desired angle by displacing the edge of the slice lip ahead or behind the edge of the apron by turning the front wall around a pivot shaft positioned near the seal between the front wall and the top wall. Hereby the gap between the front wall and flow resisting unit inside the head box becomes changed. It is necessary subsequently to adjust said flow resisting units in order to have said gap re-established to correct dimension.

All these types of head boxes, especially such with high pressure, have the disadvantage that the front wall is subjected to a considerable load which in large highspeed machines may amount to about one hundred tons and even more. This causes a deflection of the front wall which is difficult to avoid, particularly at large walls. The deflection created in the front wall causes changes in the slice outlet and disturbs thereby the adjustment of the stock stream.

This invention has made it possible to eliminate disadvantages.

According to the invention the front wall of the head box is mainly characterized thereby that said front Wall is divided into a movable wall part, adapted to adjust the slice outlet, and a fixed wall part, adapted to take up the largest part of the head box load, said movable wall part being positioned entirely inside the head box in such a way, that the pressure prevailing within said box comes to act on both sides thereof, i.e. also in the space between said movable part and said fixed part of the wall.

said

Further features of the invention will appear from the following description and with reference to the accompanying drawing which shows a vertical section of a preferred embodiment of a stock head box with a front wall according to the invention.

The front wall of the head box is divided into two parts, that is a movable part 1 and a fixed part 2. The movable part 1 is positioned inside the head box and subjected to pressure at both sides. The fixed wall part 2 takes up the principal part of the load in the head box. The lower edge of the movable part 1 forms a slice lip 10. A fixed apron element 7 forms together with the lip 10 a slice outlet 4. The stock stream flows through said slice onto a wire 11, whereby the point of contact between the stock flow and the wire may be adjusted with respect to the breast roll by displacing the breast roll horizontally.

The movable wall part 1 and the fixed wall part 2 are connected to each other by means of a flexible sheet 3 such as a rubber sheet permitting said wall parts to move with respect to each other. Since said sheet may be firmly fixed to both front wall parts and only moves relatively the side walls of the head box it will merely be necessary to contact between the flexible sheet and the sides of the head box. The rubber sheet 3 is preferably fastened to the fixed wall part 2 and the movable wall part 1 at the same level and in such a way that the rubber sheet in the space between these wall parts will get a downwards convexly rounded form.

The movable wall part 1 is turnable around the axle 8, carried in bearings supported by the side walls, said bearings being located approximately on the same level as the upper edge of the perforated bafile 6 in such a way that the gap between the wall part 1 and said bame unit 6 remains substantially unchanged when the movable wall part1 is turned. In known devices the pivot shaft is arranged close to the top edge of the front wall,

whereby the gap between the front wall and the flow resisting unit changes in such a degree that it is necessary to displace the bathe in order to re-establish the gap to its original size. The thickness of the stock stream may also be regulated by raising or lowering the movable unloaded part 1.

What I claim is:

A front wall for a closed stock head box, especially a high pressure head box, for the adjustment of the stock stream flowing onto a forming wire through an outlet opening or slice, comprising a horizontal pivot shaft, a rigid wall part fixed to the ceiling of said box and a movable wall part located substantially parallel to said rigid wall part and turnable around said horizontal pivot shaft, the bottom edge of said movable wall part being arranged to provide the upper lip of the slice, said movable wall part being connected to said rigid wall .across the entire width of the stock head box by means of a downwardly bent sheet of impervious flexible material, said flexible sheet being fastened to the bottom free edge of said rigid wall part and to said movable wall part at the same level.

References Cited in the file of this patent UNITED STATES PATENTS 2,381,286 Hornbostel Aug. 7, 1945 2,750,854 McArn June 19, 1956 2,784,651 Hornbostel Mar. 12, 1957 2,881,674 Johnson et al. Apr. 14, 

